Well, there are other forms of Hydrangea that would probably work
although most of them really want moisture and fair-to-good
soil.

One which is likes shade or morning sun (according to one of my books)
is oak-leaf hydrangea:
http://plants.usda.gov/java/profile?symbol=HYQU3
Native to southern TN and south, but sometimes grown in cultivation
north of there.

Someone also suggested Callicarpa americana. That's a pretty plant
(well, based on the photos; we don't have one yet).
http://plants.usda.gov/java/profile?symbol=CAAM2
Native range is similar (southern TN and south), although not quite
identical. In cooler climates (zone 6 or so) it will die back to the
ground in winter, but come back from roots. Comes back quickly after
pruning. Drought tolerance is not clear from my books but I'm
guessing it would come back pretty well after most kinds of trauma.

I don't know, these are just a few possibilities among many.

For reference, you might look at http://www.sunlightgardens.com which
is a grower of native plants a few miles up the road from me. They
specialize in natives of the eastern US and you can probably get some
ideas there.

That looks like a great place to browse.

Not everything in their catalog is native, but most are. And for the
most part they are pretty good at telling you where the plant is from.